Continuous absorption refrigeration



May 7, 1935.

E. ALTEKIRCH 2,000,005

CONTINUOUS ABSORPTION REFRIGEHATION Original Filed Nov. 27, 1929Patented May 7, 1935 l CONTINUOUS ABSORPTION REFRIGERATION EdmundAltenkirch, Neuenhagen, mear Berlin,

Germany, assignor to The Hoover Company, North Canton, Ohio, acorporation of ohio Original application November 27, 1929, Serial No.410,020. Divided and this application October 6, 1933, Serial No.692,373. In Germany November. 30, i928 9 Claims.

This invention relates to continuous atnorption. refrigeratingapparatus, and more particularly to the boiler or generator and theabsorber and the manner in which these devices cooperate with the otherparts of the refrigerating system. This application is a divisional caseof U. S. application Serial No. 410,020 led November 27,

1929, issued asPatent No. 1,951,336 onMarch 20,

1934 for process and apparatus for heat exchange between two currents ofgas. An application corresponding to application Serial No. 410,020 wasfiled in Germany November 30, 1928.

In continuous absorption refrigerating systems operatingr with ammoniaor other refrigerant of l5 frigerant is considerably higher in theboiler than m the other parts of the system, considerable difficulty hasbeen experienced in successfully operating the unit on account ofcorrosion. The metal of which the apparatus is constructed is apt todecompose in those parts of the system where it is subjected to the uidsat high temperature and vapor pressure.

It is an object of the present invention to provide a boiler system ofsuch a nature that it may operate at a comparatively low temperature.

, Thus corrosion is largely prevented.

It is a further obj ect of the invention to provide a novel combinationof boilers and absorbers which will permit the refrigerating apparatusto operate under conditions tending to reduce the amoimt of corrosion.

It is a further object of the invention to provide a novel refrigeratingapparatus employing an inert gas or other auxiliary pressure equalizingmedium, in which the inert gas is circulated over more than a singlepath so as to improve the operation of the unit.

It is a further object to provide a' `refrlgerating apparatus soarranged as to enable the absorber to operate under the favorablecondition of a low solution concentration range while the boileroperates under the favorable condition of a high concentration range.

Other objects and advantages reside in novel features of the arrangementand construction of parts and will be apparent from a consideration ofthe following description taken in connection with the accompanyingdrawing in which:-

The single figure of the drawing is a diagrammatic representation of acontinuous absorption refrigerating system constructed in accordancewith the principles of the present invention.

The continuous absorption refrigerating .system illustrated in thedrawing consists of a main like nature Where the vapor pressure of thereboiler 4i, of usual construction, a gas separation chamber 43, asecond or auxiliary boiler 50, a condenser 45, an evaporatorv 48, anabsorber 52, and a second absorber 58, these parts being connected byvarious conduits to form the complete 5 system.'

A pipe 42 of small diameter constitutes a gas life pump of the usualconstruction for conveying refrigerant gas 'and absorption liquid fromthe main boiler 4I into the gas separation cham- 10 ber 4,3. Therefrigerant gas is conveyed from the gas separating chamber 43 to thecondenser 45 by means of a gas conduit 44. In the condenser 45 therefrigerant gas is liquefied and conveyed by means of a U-pipe 46 and asmall cham- 15' ber 4l into the evaporator 48.

The evaporator 48 may be of the usual construction consisting merely ofa cylindrical vessel provided with a number of bailie plates therein.

'I'he auxiliary boiler 50 consists merely of a 20 closed vessel providedwith baies and with some means for heating it. It is connected to thegas separating chamber 43 by a` U-shaped conduit 49. The conduit 49serves to convey absorption liquid from the bottom of the gas separation25 chamber 43 to the top-.of the auxiliary boiler 50.

The boiler 4|, the gas separating chamber 43 and the auxiliary boilertogether with the connecting conduits, constitute what may be called atwo-stage or compound boiler, the operation of 30 which will bedescribed later.

A U -shaped conduit 5I conveys absorption liquid from the bottom of theauxiliary boiler 50 to the top of the main absorber 52. I

The absorber 52 may be of the usual type con- 35 sisting merely of acylindrical vessel provided with a number of baie plates.

Inert gas is circulated between the evaporator 48 and the main absorber52 by means of the gasf conduits 53 and 54, these gas conduits being in40 heat exchange relation over a portion of their length as indicated at55. For draining liquids which may collect in the bottom of theevaporator back to the absorption liquid circulation system, a smallU-shaped conduit 56 connects the 45 bottom of the evaporator to thehorizontal por- Ation of the gas conduit 54.

The botom of the main absorber 52 is connected to the top of theauxiliary absorber 58 by means of a conduit 51. This conduit not only 50serves to drain absorption liquid from the main absorber 52 to theauxiliary absorber 58 but it is also of sufcient size to permit gases toilow from one absorber to the other. The conduit thus acts as anequalizer or means for maintaningthe total pressure in the absorber 58the same as that in the absorber 52.

The auxiliary absorber 58 may be similar to the main absorber 52 andconsist merely of a cylindrical vessel provided with a number of baiiieplates.

For conveying absorption liquid from the auxiliary absorber 58 back tothe main boiler 4|, the U-shaped conduit 59 is provided, this conduitpassing in heat exchange relation with portions of the liquid conduits49 and 5|.

Inert gas is also circulated between the auxiliaryA boiler 5U and theauxiliary absorber 58, this being accomplished by means of the gasconduits 60 and 6|, the upper portions of which are in heat exchangerelation.

To promote this circulation a jet 62 may be provided in accordance withknown practices, this jet being supplied with refrigerant gas Vcomingfrom the gas separation chamber 43.

Assuming that the system just described is charged with ammonia asrefrigerant, water as absorption liquid and hydrogen as inert gas, andthat heat is applied to the boilers 4| and 50, four separate cycles ofcirculation will be set up, one for the refrigerant, one for theabsorption'liquid and two for the inert gas.

The refrigerant will pass over a cycle (neglecting that part passingthrough the Jet 62) as follows:

Starting with the boiler the refrigerant will pass upwardly through thegas lift pump conduit 42, the gas separation chamber 43, the gas conduit44, a portion of which may act as a rectifier, condenser 45, the supplyconduit 46, vessel 41, the evaporator 48, in which the refrigerant willevaporate and be conveyed by the inert gas through the conduit 54 intothe rst absorber 52, and thence through the conduit 51 into the secondabsorber 58. In the absorbers 52 and 58 the refrigerant will be absorbedand conveyed back into the boiler 4| through the conduit 59.

, The absorption liquid will pass through a cycle starting with theboiler 4I upwardly through the gas lift pump conduits 42, the gasseparatio'n chamber 43 from which it will flow through the conduit 49into the auxiliary boiler 50 and from there into the top of the absorber52 through the conduit 5|. After trickling down over the baille platesin the main absorber 52 the liquid will pass through the conduit 51 intothe auxiliary absorber 58. After trickling downwardly over the baffleplates therein it will be conveyed back to the boiler 4| through theconduit 59.

One of the inert gas circuits will be between the evaporator .'48 andthemain absorber 52, the' gas leaving the top of the evaporator and flowingto the bottom of the absorber 52 through the conduit 54 and afterpassing upwardly through the absorber 52 flowing back to the lowerportion of'the evaporator through the gas conduit 53. A

Another inert gas circuit is, as mentioned above, between the auxiliaryboiler 50 and the auxiliary absorber 58. The gas in this circuit isimpelled by the refrigerant` gas passing through the jet 62. The inertgas leaves the top of the auxiliary boiler 50 and iiows into the'bottomof the auxiliary absorber 58 through the conduit 6|. It

then returns to the lower portion of the aux,

iliary boiler 50, after passing upwardlyover the plates in the auxiliaryVabsorber58, through the gas conduit 60.

As stated above, heat is applied` to the main boiler 4|. Heat isalsoapplied to the auxiliary boiler 50 and it is in this respect thatthe system differs from the usual ammonia absorption system using aninert gas.

In the system illustrated the refrigerant vapor expelled in the mainboiler 4| is condensed in the condenser 45, evaporated in the evaporator48 and conveyed to the absorber 52 by an inert gas circuit just the sameas in the known types of condensing ammonia absorption systems. The Weaksolution leaving the main boiler 4I, however, is conducted to the inertgas filled boiler 50, in which the solution concentration is furtherdecreased by vaporizing the refrigerant into the inert gas stream at atemperature which may be either the same as that ofthe main boiler 4| oreither higher or lower than the temperature of the main boiler, theboiler 50 operating at a lowerI refrigerant vapor pressure than theboiler 4| due to the presence of inert gas in the boiler 50. Therefrigerant vapor expelled in the auxiliary boiler 50 is not put to anyuseful work in so far as refrigeration is concerned, but is absorbedback into the solution in the auxiliary absorber 58 following the mainabsorption process in the absorber 52. The advantage gained by the useof the compound boiler andabsorber results from the fact that because ofthe employment of the auxiliary boiler 50, the absorption liquidsupplied to the main absorber 52 through the conduit 5| is considerablyweaker than would otherwise be the case.

It will thus be seen that means for supplying a refrigerant at a lowconcentration to the main absorber is provided without the necessity ofheating the absorption liquid in the boiler system to a hightemperature. Because of the fact that corrosion and decomposition takeplace in systems of this nature much more rapidly at high temperatures,any feature which tends to reduce the boiler temperature withoutadversely affecting the operation of the unit as a whole, is highlydesirable. Thus 'me advantage of the present system becomes apparent.Another advantage results from the fact that the main absorber 52 mayoperate at a lower temperature than usual and thus facilitatesabsorption of the refrigerant from the evaporator.

In order to illustrate the advantages of the present invention anexample is given of its application to an air cooled system usingammonia, water and hydrogen asl fluids and operating under somewhatstandard test conditions.

Assuming that it is desirable to operate the main absorber 52 at atemperature around 120 degrees F. so that it may operate satisfactorilyin a 100 degrees F. room, the present invention makes it possible tosupply the absorption liquid to the absorber 52 at a concentration ofabout l10%. This would permit an absorption solution concentration rangefrom 10% to 25% in the absorber 52 and would give excellent results inso far as absorption is concerned. However, if

this range were employed in the usual continuous inert gas type ofsystem using ammonia as refrigerant, a boiler temperature `oi'approximately 380 degrees would be required, assuming the concentrationrange indicated above, butY would operate over a concentration range of,say from 35% down to 22 5% concentration.

The auxiliary boiler 50 and the auxiliary absorber 58 make thisdifference in concentration ranges possible,.the auxiliary boilerloweringv the concentration `of the solution passing to the mainabsorber from 22.5% to and the auxiliary absorber 58 raising theconcentration of the solution passing through it from 25% to 35%. At thetotal pressure noted above, the auxiliary boiler temperature need not behigh to accomplish this further reduction in the solution concentration,a temperature around 260 F. being high enough due to the fact that therefrigerant Vapor pressure in the auxiliary boiler hasbeen reduced, dueto the pressure of the inert gas therein, down to as low as 80 poundsper square inch, absolute.

No diiliculty is experienced in absorbing the refrigerant expelled inthe auxiliary boiler, back into the solution in the auxiliary absorber,be-

cause the latter may operate at a temperature higher than the mainabsorber without adversely affecting the operation of the unit as awhole. Satisfactory operation may be obtained in the example given withthe main absorber operating at a temperature around 120 F., as notedabove,

and the auxiliary absorber operating at a temperature in theneighborhood of 130 F. The refrigerant vapor pressure in the auxiliaryabsorber is, of course, correspondingly higherin the auxiliary absorberthan in the main absorber.

A Thus in the example illustrated the boiler temperature might bereduced 60 degrees AF., that is, from 380 degrees to 320 degrees, by theapplication of the-present invention to a known type of refrigeratingapparatusV operating under normal conditions.

It is apparent that certain features of the invention are applicable tovarious types of refrigerating apparatus such as those in which aresorber is used instead of the condenser illusl the auxiliary boiler tothe main absorber, from the main absorber to the auxiliary absorber andfrom the auxiliary absorber back to the main boiler, means for expellingrefrigerant from the solution in the main boiler, for causing the sameto produce cooling effect' and for conveying the Same into the mainabsorber, means for expelling lrefrigerant from `the solution in the`auxiliary boiler to lower the concentration of the solution as itpasses from themain boiler to the main veying the refrigerant expelledin the absorber and means utilizing' inert gas for conauxiliary boilerto'theauxiliary absorber.

2. In a continuous absorption refrigerating system, the combination withanabsorber, a boiler and means for circulating absorption liquidtherebetween, of means for lowering the concentration of the absorptionliquid' as it passes from the boiler to the absorber and for raising thecon- Acentration o f the absorption lquidas it passes from the absorberback to the boiler, said means comprising an auxiliary boiler, anauxiliary absorber and means for circulating inert gas between theauxiliary boiler and the auxiliary absorber tot transfer refrigerantfrom the `'auxiliary boiler to the auxiliary absorber.

3. In a continuous absorption refrigerating system, the combination withan absorber, a boiler and means for circulating absorption liquidtherebetween, of means for lowering the concentration of the absorptionliquid as it passes from the boiler to the absorber and for raising theconl0 circulate inert gas between the auxiliary boiler A and theauxiliary absorber for expelling refrigerant from solution in theauxiliary boiler and for causing the same to be absorbed in theauxiliary absorber at a concentration range higher than that prevailingin the main absorber and lower than that prevailing inthe main boilerduring operation of the system.

4. In a continuous absorption refrigerating system, the combination withan absorber, a boiler and means for circulating absorption liquidtherebetween, of means for lowering the concentration of the absorptionliquid as it passes from the boiler to the absorber and means forraising the concentration of the absorption liquid as it passes from theabsorber back to thec boiler, said means comprising an auxiliary boiler,an auxiliary absorber and means for circulatingan inert gas in a cyclebetween the auxiliary boiler and the auxiliary absorber to transferrefrigerant from the solution in the auxiliary boiler to solution in theauxiliaryabsorber. f

5. Inv a continuous absorption refrigerating system, a compound boilerarrangement consisting of a main boiler, an auxiliary boiler, meansforcausing absorption liquid laden with refriger- 4o ant to flow throughthe lboiler arrangement, passing from the main boiler to the auxiliaryboiler, Ameans for heating the main boiler to expel refrigerant fromtheabsorption. liquid flowing therethrough and thereby lower theconcentration of the solution flowing to the auxiliary boiler, means forheating the auxiliary boiler to further lower the concentration of thesolution and means l utilizing inert gas for causing the auxiliaryboiler to operate with the refrigerant vapor pressure therein lower thanthat prevailing in the main boiler.

6. In a continuous absorption refrigerating' system, a compound boilerarrangement consisting of a main boiler, an ,auxiliary boiler, means forcausing absorption liquid laden with refrigerant; to flow through theboiler arrangement, passing from the main boiler to the auxiliaryboiler, means for heating the main boiler to expel refrigerant from theabsorption liquid flowing therethrough and thereby lower theconcentration of thelsolution flowing to the auxiliary boiler, means forheating the auxiliary boiler to further lower the concentration of thesolution and means for causing the auxiliary boiler to operate with thel refrigerant vapor pressure therein lower than that prevailing in themain boiler, said last mentioned means including conduits forcirculating an inert gas through the auxiliary boiler.

7. A continuous absorption refrigeratingvsystem 70 comprising amain'boiler, anfauxiliary boiler, a condenser, an evaporator, amainabsorber, an auxmain absorber and the evaporator and means forcirculating an inert gas through the auxiliary boiler and the auxiliaryabsorber.

. 8. In the method of refrigerating by a continuous absorptionrefrigerating. process having the steps of expelling a refrigerant froma solution, causing the expelled refrigerant to change to a more densefluid phase, lowering the vapor pressure of the condensed refrigerant tocause the same to evaporate to produce a cooling effect, and absorbingthe evaporated refrigerant ,back into the solution, the further steps ofsubjecting the weakened solution from which the refrigerant has beenexpelled to heat in the presence of an inert gas and at a refrigerantvapor pressure lower than that prevailing during the first mentionedrexpulsion to further weaken the same and causing the refrigerantexpelled by the last mentioned step to be again absorbed by thesolution.

9. In the method of refrigerating by a continuous absorptionrefrigerating process having the steps of expelling a refrigerant from asolution, causing the expelled refrigerant to change to a more dense uidphase, lowering the vapor pressure of the condensed refrigerant bybringing it into the presence of an inert gas, thereby causing therefrigerant to evaporate and produce a cooling effect and absorbing theevaporated refrigerant back into the absorption solution, the furthersteps of bringing the weakened solution resulting from the first namedexpulsion into the presence of an inert gas and` heating the same tofurther weaken the solution and conveying the mixture of inert gas andrefrigerant resulting from the last named step into the presence of theabsorption solution to cause the Irefrigerant to be again absorbed.

EDMUND ALTENKIRCH.

